Marine Bombing Squadron Six-Thirteen
October 1, 1943 - November 21, 1945
VMB-613 Insignia

PBJ-1H

Radar Gun Director Each of VMB-613's aircraft was equipped with the AN/APG-13A radar gun director for the 75mm cannon.  Commonly referred to as Falcon, it was developed by General Electric and operated on the S-band.  It was designed to provide continuous range data and elevation corrections to the pilot's gun sight, allowing for the trajectory of each 15 pound shell at ranges of up to 5,000 yards.  With this range, VMB-613's aircraft could effectively engage shipping targets while remaining outside of the range of light anti-aircraft fire.  Designed for use against shipping targets, the AN/APG-13A was not effective against most land targets as rough terrain did not allow for good target discrimination at ranges in excess of 1,500 yards.  The entire AN/APG-13A weighed approximately 105 pounds and consisted of the following:

Endfire Antenna - The most visible component, the endfire antenna, was mounted on the upper-nose of the aircraft on the axis of the 75mm cannon.  It provided a sweep of 28 degrees of azimuth and elevation. 

Indicator - The indicator was a radar scope that was operated by the copilot.  Once the pilot had identified his target, the copilot would acquire it on the indicator at about 6,000 yards.  As the run-to-target continued, the copilot would turn a crank on the side of the indicator unit to keep the range step on the radar scope lined up with the left hand side of the target echo.  This action would turn a cam which would change the angle of the pilot's optical reflector sight, thereby providing continual range corrections to the gun sight.  This eliminated the need for the pilot to estimate ranges and manually adjust the optical reflector sight. 

Range Dial - The third component, the range dial, was located near the gun sight.  Operated by the same action that adjusted the optical reflector sight, the range dial provided the pilot with the range to the target, enabling the pilot to determine when to commence firing and when to break off the attack in order to remain outside the range of light anti-aircraft fire.

Lighthouse Tube Receiver - The final component, the lighthouse tube receiver, was located under the copilot's seat.  This device received the radar signal from the endfire antenna and fed the signal to the indicator.

A diagram of the AN/APG-13A radar gun director and photographs of the indicator, lighthouse tube receiver, and range dial is provided at the following link:  AN/APG-13A Radar Gun Director

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PBJ-1H Pilot's Compartment - Port Side Thumbnail Image PBJ-1H Pilot's Compartment Thumbnail Image PBJ-1H Pilot's Compartment - Starboard Side Thumbnail Image

Pilot's Compartment

Port Side

Pilot's Compartment

Pilot's Compartment

Starboard Side

PBJ-1H Instrument Panel Thumbnail Image PBJ-1H Control Pedestal Thumbnail Image Gun Sight Thumbnail Image

Instrument Panel

Control Pedestal

Gun Sight

PBJ-1H Radio Compartment Thumbnail Image PBJ-1H Radio Compartment (Aft View) Thumbnail Image PBJ-1H Tail Turret Thumbnail Image

Radio Compartment

Radio Compartment

Tail Turret

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